1. Field of the Invention
This invention relates in general to rotary vane compressors for air conditioning systems, particularly for vehicles.
2. Description of the Prior Art
A rotary vane automotive air conditioning compressor has a compressor housing that contains a chamber with front and rear side blocks, and a cylindrical rotor that rotates on a shaft supported by bearings within the chamber. The rotor has vanes mounted to it which slide outward and inward within slots formed in the rotor. The vanes slide against the wall of an oval chamber. Refrigerant at suction pressure enters the compression chamber. The vanes compress the refrigerant before it is discharged through a valve.
In the prior art, sliding vane rotary compressors made use of the interfaces between the rotor and the front and rear side blocks to resist axial thrust loads created by electro-magnetic clutches and internal pressure. This traditional and costly design approach places severe specification requirements on the rotor/shaft assembly, the supporting radial bearings, and the two side blocks. Machining for flatness, perpendicularity, runout, and surface finish are all done to extremely small tolerances. Surface treatments to prevent the rotor from galling the side blocks must be carefully controlled during all phases of the process. To provide lubrication to the rotor/side block interfaces, small holes are drilled in the side blocks. Hot, oil-ladened discharge gas is metered to the interfaces through the small holes. Producing acceptable parts for this type of compressor is very costly and scrap rates are not insignificant.
Bearings which will support a shaft against axial thrust loads have been employed in general in industry. One type of such bearing employs two ball bearings, with the outer races engaging each other and the inner races spaced apart from each other and preloaded through the balls and outer races against the shaft. Such bearings have not been employed in refrigerant compressors to applicant's knowledge. Rather, only radial support bearings have been used, with the thrust being handled through the interfaces between the rotor and side blocks.